Non-Uniqueness of Parameters Extracted from Resonant Second-Order Nonlinear Optical Spectroscopies
| Autor: | Bertrand Busson, Abderrahmane Tadjeddine |
|---|---|
| Přispěvatelé: | Laboratoire de Chimie Physique D'Orsay (LCPO), Université Paris-Sud - Paris 11 (UP11)-Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS), Institut de Chimie du CNRS (INC) |
| Jazyk: | angličtina |
| Rok vydání: | 2019 |
| Předmět: |
Photon
Infrared FOS: Physical sciences Infrared spectroscopy 02 engineering and technology 010402 general chemistry 01 natural sciences 7. Clean energy Molecular physics symbols.namesake Physics - Chemical Physics Molecular film Physical and Theoretical Chemistry Spectroscopy Chemical Physics (physics.chem-ph) Physics [PHYS.PHYS.PHYS-OPTICS]Physics [physics]/Physics [physics]/Optics [physics.optics] 021001 nanoscience & nanotechnology Polarization (waves) 0104 chemical sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials [CHIM.THEO]Chemical Sciences/Theoretical and/or physical chemistry Dipole General Energy symbols [PHYS.PHYS.PHYS-CHEM-PH]Physics [physics]/Physics [physics]/Chemical Physics [physics.chem-ph] 0210 nano-technology Raman spectroscopy Optics (physics.optics) Physics - Optics |
| Zdroj: | Journal of Physical Chemistry C Journal of Physical Chemistry C, American Chemical Society, 2009, 113 (52), pp.21895-21902. ⟨10.1021/jp908240d⟩ |
| ISSN: | 1932-7447 1932-7455 |
| DOI: | 10.1021/jp908240d⟩ |
| Popis: | Experimental data from second-order nonlinear optical spectroscopies (SFG, DFG, and SHG) provide parameters relevant to the physical chemistry of interfaces and thin films. We show that there are in general 2 N or 2 N-1 equivalent sets of parameters to fit an experimental curve comprising N resonant features, of vibrational or electronic origin for example. We provide the algorithm to calculate these sets, among which the most appropriate has to be selected. The main consequences deal with the existence of “ghost resonances”, the need of a critical analysis of fit results, and the procedure to search for better sets of parameters coherent with applied constraints. For the past several years, infrared-visible sum-frequency generation (SFG) has become a widely used investigation technique for the chemical analysis of interfaces and surfaces. A lot of technical work has been done to improve the experimental set-ups dedicated to the production and detection of SFG photons. In the nonlinear SFG process, two monochromatic light sources (frequencies ω1 and ω2) create a second-order polarization when interacting with a material. At the lowest-order (i.e., dipolar) approximation, this polarization is proportional to the product of the incoming electric fields through the second-order susceptibility tensor � (2) , which accounts for the material’s properties. The macroscopic polarization and susceptibility account for spatial averages of microscopic second-order dipole moments and hyperpolarisabilities (� ), respectively. The secondorder polarization may oscillate at the sum (ω1 + ω2, SFG) or the difference (|ω1 - ω2|, DFG) of the incoming frequencies, acting as a coherent source of new beams at these frequencies. As such processes have a low cross section, they require the beams to have a high energy density, implying the use of short pulsed lasers. Infrared-visible SFG/DFG spectroscopy uses one beam in the visible range, usually with fixed frequency, which makes the detection of the few SFG photons easier, and a tunable (or broadband) one in the infrared (IR) frequency range. The SFG/DFG process becomes resonant (and therefore amplified) when the energy of the infrared beam matches that of an IR and Raman active vibrational transition of the material, making it a vibrational spectroscopy. The main advantage of the nonlinear vibrational spectroscopies as compared to the linear ones (e.g., IR absorption, Raman spectroscopy) lies in a fundamental property of second-order nonlinear optical (NLO) processes, which vanish within media possessing an inversion symmetry. The direct consequence is that SFG/DFG in centrosymmetric materials is only produced where the symmetry is broken, i.e. at the interface between two media. SFG/DFG spectroscopy is therefore intrinsically specific of interfaces. This has led to the continuous spreading of this spectroscopic tool over time and its application to various kinds of interfacess molecular monolayers adsorbed at the surface of liquids, 1 solids 2 and nanoparticles, 3‐6 the surface of liquids, 7 thin molecular films 8 sunder diverse environments, for example in vacuum, 9 |
| Databáze: | OpenAIRE |
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